There have been proposed many switchgear operating mechanisms that make use of an electromagnetic rebound principle. However, most of the operating mechanisms are applied to vacuum valves. Thus, the displacement of the operating mechanism corresponding to the stroke of a contact point unit, which depends on a voltage class, is relatively short, e.g., ten-odd millimeters or less.
Furthermore, in order to increase the response speed from the issuance of an electrode opening command to the start of an operation, there has been proposed an operating mechanism which includes a movable coil in addition to a fixed coil of an electromagnetic rebound mechanism and which operates with a small amount electric energy and at a high response speed.
For example, Patent Document 1 and Patent Document 2 disclose an operating mechanism which includes a switch unit, a movable coil, an electrode-opening-purpose fixed coil, an electrode-closing-purpose fixed coil and a magnetic latch mechanism. The switch unit includes a fixed electrode and a movable electrode which can be brought into contact or out of contact with each other. The movable coil is a coil fixed to an intermediate portion of a movable shaft connected to the movable electrode. The electrode-opening-purpose fixed coil is a coil which is disposed at the side of the movable electrode in the axial direction of the movable coil and which is configured to rebound between itself and the movable coil. The electrode-closing-purpose fixed coil is a coil which fixed to the opposite side of the electrode-opening-purpose fixed coil from the movable coil and which is configured to rebound between itself and the movable coil. The magnetic latch mechanism is a mechanism which makes use of a magnetic attraction force of a permanent magnet fixed to an end portion of the movable shaft.
The operating mechanism using such a magnetic rebound mechanism is characterized in that it is possible to obtain a high response and a high speed. However, in contrast to the high response and the high speed, the acceleration acting in the movable unit becomes larger. It is therefore necessary to make the movable unit relatively strong.
In order to comply with such a need, Patent Document 3 proposes an operating mechanism in which a coil is fixed to a movable unit. In this prior art, there is proposed a method of bonding and reinforcing a movable coil with a resin mold or a varnish. There is also proposed a method of installing a movable coil within a nonmagnetic case to increase the rigidity thereof.
Furthermore, the electromagnetic rebound mechanism applied to a vacuum circuit breaker needs to have a function of maintaining a contact point position within a vacuum valve in an open circuit state or a closed circuit state. However, the responsiveness of such a position maintaining mechanism affects the response time of the entirety of the switchgear which makes use of the electromagnetic rebound mechanism. To cope with this, a magnetic latch mechanism which does not require a mechanical holding and releasing operation is proposed in Patent Document 4 as well as Patent Document 1 and Patent Document 2.
In Patent Document 4, an operating rod is held so that the operating rod can move in such a direction as to bring a movable contact member into contact or out of contact with a fixed contact member. Furthermore, an elastic body biases the operating rod against a movable member whose movement amount is restricted. A permanent magnet for holding and attractingly driving the movable member is installed and an operating electromagnet is fixed to the movable member. A driving-purpose spring is disposed in an end portion of the movable member and is used as a drive source in a circuit-opening operation direction.
Furthermore, a technique of properly restraining the high-speed operation of the electromagnetic rebound mechanism is disclosed in Patent Document 5. In this technique, similar to Patent Document 1 and Patent Document 2, fixed coils are disposed at the electrode-opening-position side and the electrode-closing-position side. For example, in an electrode-opening operation, a pulse current flows through a contact-point-side fixed coil. A movable contact point and a movable unit operate in an electrode-opening direction. Immediately before the end of the electrode-opening operation, a pulse current flows through another fixed coil, thereby generating an electromagnetic rebound force so as to restrain the operation. Thus, a brake force acts on the movable unit, whereby the movable unit as a whole stops.